Thianthrene Radical Cation Hexafluorophosphate
Johannes Becka , Thomas Bredowb , and Rachmat Triandi Tjahjantoa
a
b
Institute of Inorganic Chemistry, Bonn University, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
Institute for Physical and Theoretical Chemistry, Bonn University, Wegelerstr. 12, 53115 Bonn,
Germany
Reprint requests to Prof. Dr. J. Beck. Fax: +49 (228) 73 5660. E-mail: [email protected]
Z. Naturforsch. 2009, 64b, 145 – 152; received September 16, 2008
In the presence of [NBu4 ][PF6 ] as the electrolyte, thianthrene (TA) is transformed by electrochemical oxidation to thianthrenium hexafluorophosphate containing the TA•+ radical cation. The reactions
were performed in CH2 Cl2 , H3 CCN, and liquid SO2 as solvents. In CH2 Cl2 , TA[PF6 ] is sparingly
soluble and is deposited directly in crystalline form on the platinum electrode. In H3 CCN and liquid SO2 , TA[PF6 ] is highly soluble and gives dark blue solutions from which it can be crystallized
upon concentration of the solutions. The air sensitive crystals are black with bronze metallic luster.
They belong to the monoclinic system (C2/m, a = 12.4345(8), b = 10.5318(6), c = 11.1303(7) Å,
β = 112.565(3)◦ ) and are built up of almost planar TA•+ cations and octahedral [PF6 ]− anions. The
F atoms of the anions are disordered over two positions. The radical cations are associated to form
dimeric units (TA•+ )2 with the planar molecules stacked with two weak S· · · S bonds (3.06 Å). In
the crystal these dimers are separated by the [PF6 ]− anions. Electrical conductivity measurements
show TA[PF6 ] to be a small-gap semiconductor. Conductivity is low at r. t. but reaches 2.5 · 10−5 S
m−1 at 110 ◦C, the activation energy in the high-temperature region amounts to 1.2 eV. Periodic
quantum-chemical calculations at hybrid density-functional level predict a strong coupling between
neighboring (TA•+ ) spin centers, resulting in a singlet ground state. The calculated band gaps of both
singlet (1.5 eV) and triplet (0.9 eV) states are small, consistent with the measured conductivity.
Key words: Thianthrene, Radical, Hexafluorophosphate, Conductivity, Band Structure,
Crystal Structure
Introduction
For more than one hundred years the intensive color
of solutions of thianthrene (TA) in sulfuric acid has
been known which is caused by the oxidation of TA
to the radical cation TA•+ under release of SO2 [1].
The neutral molecule is non-planar and bent along the
intramolecular S· · · S axis by 131◦ as determined by
electron diffraction in the gas phase [2], and by 128◦
as determined by single crystal X-ray diffraction [3].
Several theoretical calculations were reported dealing
with the molecular conformation in gas-phase and solution and its interpretation [4 – 8].
Molecular structure of thianthrene (TA).
Different ways for oxidation of TA to the radical
cation have been reported. These include the reaction
of TA with perchloric acid in hot acetic anhydride [9],
the reaction of TA with its monoxide in nitromethane
and perchloric acid or tetrafluoroboric acid [10], the
reaction of TA and ICl in carbon tetrachloride [11],
the reaction of TA with SbCl5 in chloroform [12],
the reaction of TA with NO[BF4 ] in acetonitrile [13],
and the reaction of TA with AlCl3 in methylene chloride [14]. The structure determination of thianthrenium
tetrachloroaluminate revealed the significant structural
change caused by the oxidation. In contrast to the bent
neutral molecule, the radical cation turned out to be almost planar [14]. This is interesting since the odd number of electrons does not meet Hückel’s 4n + 2 rule for
an aromatic system. As found by the structure determination, the radical cations in (TA•+ )[AlCl−
4 ] form
dimers in the crystal. This tendency to dimerize was already known from studies of solutions. By visible light
absorption spectra and in situ ESR spectroscopy in solution the formation of dimers could be shown to be
strongly dependent of the solvent [15], concentration
and temperature [16].
The molecular arrangement of planar molecules in
the crystalline state depends on many parameters and
is in general hard to predict. Even such a long known
c 2009 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com
0932–0776 / 09 / 0200–0145 $ 06.00 Unauthenticated
Download Date | 6/16/17 4:35 AM
146
J. Beck et al. · Thianthrene Radical Cation Hexafluorophosphate
organic radical ion like thianthrenium can bring a surprise. The oxidation of TA with the dodecamethylboranyl radical yielded (TA)3 (B11 (CCH3 )12 )2 containing
a thianthrene triple-decker (TA)2+
3 carrying two positive charges with a unique tilted position of the middle
molecule [17].
Liquid SO2 had already turned out as a suitable
solvent for redox processes involving aromatic heterocyclic molecules. Cyclic voltammetry at −40 ◦C in
this solvent showed TA to undergo two oxidation steps
leading to the monocation and to the dication [18].
These potentials are generally slightly solvent-dependent. In organic media differences of 10 mV for the
first and 20 mV for the second oxidation step were observed [19]. To study the influence of the solvent we
performed the syntheses by electrocrystallization both
in frequently used organic solvents and in the rarely
used liquid SO2 . Since structural information of compounds containing unsubstituted TA radical ions is limited we concentrated our interest on the radical ion salt
of TA with hexafluorophosphate as the anion.
Results and Discussion
Electrochemical synthesis and properties of TA[PF6 ]
The electrochemical oxidation of thianthrene can
be performed in different solvents. The salt-like compound TA[PF6 ] is only sparingly soluble in CH2 Cl2
with the consequence that TA[PF6 ] formed during applying electrical current is deposited on the surface of
the electrode. A polycrystalline layer is generated on
the platinum wire which can be isolated in the glove
box. In CH3 CN and liquid SO2 TA[PF6 ] is well soluble. In these solvents the solution in the anodic part
of the cell turns dark blue and even after prolonged
electrolysis no deposition on the electrode or precipitation of solid material occurs. TA[PF6 ] was isolated
by distilling off the solvent and, in the case of CH3 CN,
allowing diethyl ether to diffuse into the concentrated
solution. In the case of liquid SO2 , the solvent was released as a gas at r. t., and after concentration to one
third of the original volume black crystals of bronze
metallic luster appeared on cooling the solution. X-Ray
powder diffractograms revealed the identity of all isolated samples and the identity with the crystal selected
for the single crystal structure determination.
Cyclic voltammetry measurements of thianthrene
in liquid SO2 were so far reported only at low temperatures (−40 ◦C) below the boiling point of this
solvent [18]. We determined the oxidation potentials
Fig. 1. Cyclic voltammetry diagrams of thianthrene in liquid SO2 with [NBu4 ][PF6 ] as electrolyte. A: an average
of 5 scans at r. t. with ferrocene (Fc) as the reference redox
system (Fc/Fc+ marked with ∗ ), B: pure thianthrene (single
scans) at different temperatures.
again at ambient temperature to come close to the actual reaction conditions. Fig. 1a shows the cyclovoltamogram of TA in liquid SO2 at 23 ◦C. Ferrocene
(Fc) was used as a reference redox system [20]. The
difference between the potential of the first oxidation
wave of TA and Fc/Fc+ under the applied conditions is
0.858 V. The observed potential for the first oxidation
step does not differ significantly from that in acetonitrile which was measured to be 0.846 V vs. Fc/Fc+ .
On varying the temperature of the SO2 solution from
−63 ◦C to ambient temperature we observed a significant shift of the first oxidation wave by about 0.1 V
to higher potentials (Fig. 1b). The potentials that had
to be applied to oxidize TA in the respective solvents
for the synthesis of the radical cation showed remarkable differences. In acetonitrile and dichloromethane
a potential of 4 V between the electrodes was necessary for the occurrence of a persistent violet color of
the solution and the deposition of TA[PF6 ] on the electrode, while in SO2 just 2 V were sufficient. Despite
Unauthenticated
Download Date | 6/16/17 4:35 AM
J. Beck et al. · Thianthrene Radical Cation Hexafluorophosphate
the applied high potentials in the organic solvents, no
formation of the dication TA2+ was observed which
is known as the component of tetramethylthianthrenium(2+) hexachloroantimonate [21].
TA[PF6 ] is highly sensitive to oxidation in solution
and in the solid state and can only be handled in an
argon-filled glove box. The visual melting point was
140 – 143 ◦C. In the DSC measurements, however, a
broad endothermic process is observed with an onset temperature of 126 ◦C indicating decomposition.
Different samples of TA[PF6 ] all showed a small endothermic process on heating to 80 ◦C with a heat conversion of 0.36 kJ mol−1 . This process seems to be irreversible since on cooling a corresponding exothermic
process could not be unequivocally detected. The nature of this transition remains unknown.
Crystal structure
The crystal structure of TA[PF6 ] is built up of almost
planar thianthrenium radical cations and of octahedral
hexafluorophosphate anions. The planarity of TA•+
cations is typical for thianthrenium radical ions. The
cations are bisected by mirror planes through the bonds
C3–C3I , C1–C1I , C4–C4I and C6–C6I (Fig. 2). Each
cation therefore has crystallographic Cs symmetry. The
point group C2v is, however, almost fulfilled. The two
sulfur atoms and the atoms of each one of the two benzene rings form well-defined planes. The largest deviations form the best plane through S, SI , C1, C1I , C2,
C2I , C3, C3I are observed for C1 and C1I with 0.040 Å
and for the plane S, SI , C4, C4I , C5, C5I , C6, C6I for
C4 and C4I with 0.034 Å. These two planes include
a dihedral angle of 172.6◦ indicating the molecule to
Fig. 2. The thianthrenium radical ion in the structure of
TA[PF6 ]. Displacement ellipsoids are scaled to include a
probability density of 40 %. Hydrogen atoms are drawn
with arbitrary radii. Selected bond lengths (Å) and angles (deg): S–C1 1.720(2), S–C4 1.719(2), C1–C2 1.398(3),
C1–C1I 1.412(4), C2–C3 1.367(3), C3–C3I 1.398(5), C4–
C5 1.403(3), C4–C4I 1.413(4), C5–C6 1.363(3), C6–C6I
1.400(5); C1–S–C4 107.1(1), C1I –C1–S 126.09(7), C4I –
C4–S 126.08(7), C–C–C within aromatic rings 114.7(2) to
120.7(2). Symmetry operation: I = x, −y, z.
147
Fig. 3. A dimer of two thianthrenium radical cations in the
structure of TA[PF6]. Displacement ellipsoids are drawn at
the 40 % probability level. The lengths of the S· · ·S contacts
between the molecules amount both to 3.066(2) Å. Symmetry operation: III = 1 − x, y, 1 − z; IV = 1 − x, −y, 1 − z.
be almost flat but slightly bent on the S· · · SI axis. The
respective angle in the structure of TA[AlCl4 ] amounts
to 171.8◦ [14] which shows the similarity of the radical
ions in both structures. The radical ions are associated
to form dimers (Fig. 3). The two molecules of each pair
are related by a twofold axis. Together with the mirror
plane each dimer gains crystallographic C2h symmetry,
but is only slightly distorted from the higher symmetry
point group D2h . The two identical S· · · S intermolecular distances amount to 3.066 Å which is in between
a covalent S–S bond (2.08 Å) and the van der Waals
distance of two sulfur atoms (≈ 3.6 Å). The dimers are
isolated from each other. The shortest S· · · S distances
between sulfur atoms of neighboring (TA•+ )2 dimers
are longer (3.743 Å) than the sum of the van der Waals
radii.
In (TA•+ )[AlCl4 ]− the thianthrenium ions show
ring slippage. Two different intermolecular S· · · S distances of 3.05 and 3.11 Å were found, and the
S· · · S· · · S angles in the four-membered ring of sulfur
atoms amount to 98◦ and 82◦ [14]. In (TA•+ )[PF6 ]−
the two thianthrenium radicals are in perfect overlap,
and due to the local symmetry the four S· · · S· · · S angles are strictly rectangular. The interactions between
molecular π -conjugated radicals can be divided into
σ and π bonding [22]. For thianthrene a σ dimer is
expected to exhibit a substantial bending at the intramolecular S· · · S axis and short intermolecular S–S
bonding in the region of the length of a single bond.
With almost flat molecules and quite long S· · · S bonds
the dimers in the structure of TA[PF6 ] are true π
dimers.
In the hexafluorophosphate anion each F atom position is split into two equally occupied positions indicating a disorder of the ion. The PF6 octahedra have
the same center of gravity within the P atom but have
different orientations (Fig. 4). The P–F bond lengths
Unauthenticated
Download Date | 6/16/17 4:35 AM
148
J. Beck et al. · Thianthrene Radical Cation Hexafluorophosphate
Fig. 4. The hexafluorophosphate ion in the structure of
TA[PF6 ]. Displacement ellipsoids are drawn to include a
probability density of 40 %. The F atoms are disordered each
over two positions resulting in two half occupied, superimposed [PF6 ]− octahedra, drawn in white and grey. Symmetry
operation: II = x, 1 − y, z.
Fig. 5. The unit cell of thianthrenium hexafluorophosphate.
Atoms are drawn as spheres with arbitrary radii. The disordered [PF6 ]− anions are represented as massive polyhedra.
Fig. 6. The upper graph shows the electrical conductivity vs.
temperature for a cylindrical sample of TA[PF6] measured
by the two-probe technique. In the diagram on the bottom
an Arrhenius plot ln(conductivity) vs. reciprocal temperature
is shown. There are two regions present which can each be
fitted by a linear function.
are in the range from 1.559(3) to 1.603(3) Å. Each one
of the two superimposed hexafluorophosphate anions
is almost perfectly octahedral.
In the unit cell each radical cation dimer (TA•+ )2 is
surrounded by twelve [PF6 ]− ions which are grouped
into six pairs of closely neighboring anions (Fig. 5).
Accordingly, each pair of [PF6 ]− anions has six neighboring (TA•+ )2 cations. The overall arrangement of
the ions in the crystal structure adopts the simple rock
salt type if the (TA•+ )2 dimers are counted as the
cations and each closely neighboring pair of [PF6 ]−
are counted as one anion. The shortest intermolecular
C–H· · · F hydrogen bond (H3· · · F4, III = 0.5 + x, −0.5
+ y, 1 + z) amounts to 2.435(4) Å.
readily increases with rising temperature and reaches
2.5 · 10−5 S m−1 at 110 ◦C. The temperature dependence of the conductivity is presented in Fig. 6 and
can be described using the Arrhenius law ln σ = A
exp(Ea /kT ). The function ln σ = f (T −1 ) in Fig. 6
shows two linear regions, a steep region between 70
and 110 ◦C and a flattish region between 20 and 50 ◦C.
The overall conductivity can reasonably be described
by the superposition of two thermally activated processes in an intrinsic high-temperature region with an
activation energy of 1.2 eV and an extrinsic low-temperature region with low activation energy of 0.2 eV.
The thermal activation energy of 1.2 eV is relatively
high but can be understood considering the arrangement of the radical molecules in pairs which prevents
the presence of a conducting, half-filled crystal orbital.
Electrical conductivity
Band structure calculations
TA[PF6 ] is a small-gap semiconductor. The absolute
conductivity is very small at r. t. (5 · 10−8 S m−1 ) but
The electronic structure of TA[PF6 ] was studied theoretically at the density-functional theory (DFT) level.
Unauthenticated
Download Date | 6/16/17 4:35 AM
J. Beck et al. · Thianthrene Radical Cation Hexafluorophosphate
149
Fig. 7. Calculated band structure of the primitive TA[PF6 ]
unit cell in the singlet state (PW1PW, TZVP basis set); band
energies are given in atomic units; 1 a. u. = 27.21 eV; the
Fermi level and the bottom of the conduction band are indicated by dashed lines.
Lattice energy and band structure calculations were
performed with the crystalline orbital program C RYS TAL 06 [23]. Lattice parameters and atom positions
were taken from the experiment and kept fixed. In
C RYSTAL the Bloch functions are expanded in atomcentered basis functions. All-electron Gaussian basis
sets of triple zeta valence plus polarization (TZVP)
quality were used. The original TZV basis sets of
Ahlrichs et al. [24] were slightly modified. The most
diffuse s and p shells of the carbon and phosphorus atoms were removed in order to avoid linear dependencies of the basis. Polarization functions (p for
hydrogen, d for phosphorus, sulfur, carbon and fluorine) were added. The hybrid exchange-correlation
functional PW1PW [25] was employed. In earlier work
it was shown that Hartree-Fock DFT hybrid methods
give an improved account of electronic properties in
oxides and other compounds compared to standard
DFT methods [26]. The C RYSTAL standard values for
integral accuracy were increased by a factor of ten.
Integration in reciprocal space was performed using
a 6 × 6 × 6 Monkhorst-Pack k-point net (resulting in
112 points in the irreducible Brillouin zone IBZ). Both
singlet and triplet states were studied for the primitive cell containing two TA•+ units. With PW1PW the
singlet state is 0.7 eV/unit cell more stable than the
triplet state, indicating strong coupling between neighboring TA radicals in the same cell. It has to be mentioned, however, that the singlet-triplet energy splitting
is strongly dependent on the Hamiltonian. With the
same computational setup, the Hartree-Fock method
predicts the triplet state to be more stable by 0.4 eV,
and a standard GGA (generalized gradient approximation) functional such as PBE [27] favors the singlet state by 1 eV. As it is well known that open-shell
Fig. 8. Calculated band structure of the primitive TA[PF6 ]
unit cell in the triplet state (PW1PW, TZVP basis set); (a) α electrons, (b) β -electrons.
systems are overly stabilized at the Hartree-Fock level
whereas GGA DFT methods have a bias towards spin
pairing, hybrid methods such as PW1PW are probably a reasonable compromise. A rigorous treatment at
multireference ab initio level is required to tackle the
question of the correct ground state of this system. This
is beyond the scope of the present study.
Therefore in the following we discuss the calculated band structures of both multiplicities as shown
in Figs. 7 and 8. Irrespective of multiplicity and spin,
all bands have a rather small dispersion, indicating
weak interaction between TA dimers in different unit
cells. For the singlet state (Fig. 7) the maximum of
the valence band (VB) and the minimum of the conduction band (CB) coincide at the C point of the IBZ
(0,1/2,1/2 > in the conventional setting). The direct
C–C interband transition energy is 1.5 eV. This would
classify TA[PF6 ] as a small-gap semiconductor.
For the majority spin component (denoted as α ) of
the triplet state (Fig. 8) the maximum of the valence
band is at the Γ point (indicated as G) while the minimum of the conduction band is at the C point, similar
as in the singlet state. The difference between minimal
indirect (Γ -C) and direct (Γ -Γ ) transition is, however,
rather small. The α band gap is 3.2 eV. The valence
band maximum and the conduction band minimum of
the minority spin component (β ) are both at the B point
(<1/2,0,1/2>). Here, the calculated band gap is much
smaller than for the majority component, 0.9 eV.
Unauthenticated
Download Date | 6/16/17 4:35 AM
150
J. Beck et al. · Thianthrene Radical Cation Hexafluorophosphate
Conclusion
Table 1. Crystal structure data for TA[PF6 ].
Thianthrene (TA) can be oxidized electrochemically
to the persistent radical cation TA•+ and isolated in
crystalline form as the hexafluorophosphate salt by
using [NBu4 ][PF6 ] as the electrolyte. The formation
of TA[PF6 ] is independent of the solvent used, either
CH3 CN, CH2 Cl2 , or liquid SO2 . The salt is stable up
to 120 ◦C and shows electrical semiconduction with
a thermal activation energy of 1.2 eV in the intrinsic high-temperature region above 70 ◦C. The structure contains (TA•+ )2 π dimers with two of the planar molecules stacked coincidently in a dimer with two
weak S· · · S bonds of 3.06 Å. These dimers are isolated in the crystal and separated by the anions which
explains the semiconductivity. Theoretical calculations
at hybrid density-functional level predict that TA[PF6 ]
has a small band gap of 1.5 eV in the singlet ground
state and of 0.9 eV in the excited triplet state, respectively. Both values are consistent with the observed
conductivity.
Formula
Mr
Crystal size, mm3
Crystal system
Space group
a, Å
b, Å
c, Å
β , deg
V , Å3
Z
Dcalcd. , g cm−3
µ (MoKα ), cm−1
F(000), e
hkl range
((sin θ )/λ )max , Å−1
Refl. measured
Refl. unique
Rint
Parameters refined
R(F) / wR(F 2 ) (all refls.)
GoF (F 2 )
∆ρfin (max/min), e Å−3
Experimental Section
Thianthrene (Aldrich) was purified by recrystallization
from ethanol/toluene before use. Tetrabutylammonium tetrafluoroborate (Aldrich) was used as obtained and stored over
P4 O10 before use. All solvents were dried (CH2 Cl2 , CH3 CN,
SO2 : P4 O10 ; C2 H5 OC2 H5 : Na) and freshly distilled prior to
use.
H-shaped, two compartment glass vessels equipped with
Teflon screw cocks (Young) and a glass frit between the two
tubes were used [28]. A 2.8 mm hole was drilled through the
axes of the Teflon cocks and a stainless steel stick (3 mm diameter) was inserted through the cocks axis. This assembly
turned out to be gas-tight against the equilibrium pressure of
liquid SO2 at ambient temperature. At the end of the sticks,
platinum wires were fixed to serve as electrodes. Each compartment of this electrochemical cell had a volume of about
20 mL. In the experiments a total of 100 mg thianthrene and
400 mg [NBu4 ][PF6 ] were placed in two equal portions in the
two compartments, and about 2 × 20 mL solvent were filled
into the cell until the liquid level reached half the height of
the connecting frit.
DSC measurements were performed on 2 mg samples of
TA[PF6 ] with a type 204 F1 Phoenix (Netzsch) scanning
calorimeter. X-Ray powder diffractograms were recorded
with a Stoe Stadi P diffractometer equipped with CoKα
radiation. Conductivity measurements were performed on
pressed pellets (diameter 2 mm, thickness 0.6 mm) by the
two-probe technique. The pellet was inside a quartz tube
clamped by two steel pistons. Heating was performed by an
electrical tube oven starting from ambient temperature up to
C12 H8 F6 PS2
361.29
0.07 × 0.09 × 0.10
monoclinic
C2/m
12.4345(8)
10.5318(6)
11.1303(7)
112.565(3)
1346.0(1)
4
1.78
5.7
724
±16, ±13, ±14
0.655
13461
1632
0.082
124
0.042 / 0.102
0.96
0.48/−0.31
110 ◦C with 40 ◦C h−1 and back to ambient temperature with
the same temperature gradient. During the measurement the
polarity of the applied direct current was frequently reversed,
and all measurements were carried out twice applying a constant voltage of 1 and of 5 V.
Cyclic voltammetry measurements in liquid SO2 at ambient temperature were performed using a Metrohm µ Autolab
III analyzer in a gas- and pressure-tight glass vessel. Working and counter electrodes were made of Pt (1.65 mm2 surface area), the quasi-reference electrode was a home made
Pt/polypyrrole electrode [29], and [NBu4 ][PF6 ] was used as
electrolyte. Thianthrene (5 mg, 0.023 mmol) and [NBu4 ]
[PF6 ] (968.6 mg, 2.5 mmol) were dissolved in 10 mL of liquid SO2 ; ferrocene (4.7 mg, 0.025 mmol) was used as reference redox system. The applied scan rate was 0.2 V s−1 .
Preparation of TA[PF6 ] in CH2 Cl2
A constant voltage of 4 V was applied during four days at
ambient temperature. The anode was slowly covered with a
polycrystalline film of TA[PF6 ]. The electrode was removed
from the solution, and the layer of TA[PF6 ] was mechanically removed from the electrode in an argon-filled glove
box.
Preparation of TA[PF6 ] in CH3 CN
A constant voltage of 4 V was applied during three days at
ambient temperature. The anodic compartment gained a dark
blue color while the cathodic solution turned amber. Under a
flow of argon, the cell was opened and the anolyte transferred
to a Schlenk tube. The volume of the solution was reduced to
Unauthenticated
Download Date | 6/16/17 4:35 AM
J. Beck et al. · Thianthrene Radical Cation Hexafluorophosphate
1/3 by distilling off the solvent. The original amount of solvent volume was restored by layering the concentrated acetonitrile solution with diethyl ether. Slow diffusion of Et2 O
into the CH3 CN solution while storing at −18 ◦C caused the
precipitation of bronze-colored crystals which were filtered
off under argon. Yield: 108 mg (31.5 % of theory).
Preparation of TA[PF6 ] in liquid SO2
About 40 mL of liquid SO2 was condensed into the cell
loaded with TA and [NBu4 ][PF6 ]. A constant voltage of 2 V
was applied leading to a current of 0.2 mA. The anolyte
turned dark blue and the catholyte dark red. By slowly releasing gaseous SO2 after three days at r. t., the solutions
were concentrated to one third of the original volume. Storing at −18 ◦C for two days afforded a precipitation of dark
crystals in the anodic compartment. The supernatant solution
was filtered into the second compartment of the closed and
cold cell. The SO2 vapor was released, and 120 mg (35 %
of theory) of black, bronze-shining crystals were isolated. –
Analysis for C12 H8 F6 PS2 : calcd. C 39.89, H 2.23, S 17.75;
found C 39.83, H 2.09, S 17.60.
151
acetonitrile showed better diffraction patterns than those
from liquid SO2 . Data collection was performed at ambient
temperature using a Bruker-Nonius kappa-CCD diffractometer equipped with graphite-monochromatized MoKα radiation. The crystal structure was solved by Direct Methods and
refined using the S HELX97 programs [30]. A semi empirical
absorption correction by the multi-scan method was applied
to the data set [31]. Hydrogen atoms were refined as riding on
their attached carbon atoms with isotropic displacement factors fixed to the value 1.2 of the respective C atoms. The F
atom positions of the [PF6 ]− ion turned out to be disordered
each over two positions and were refined on split positions
with occupation factors fixed to 0.5. Crystal data and details
of the structure determinations are summarized in Table 1.
CCDC 701449 contains the supplementary crystallographic data for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data request/cif.
Acknowledgements
Crystals were selected in the glove box and fixed in capillaries which were sealed by melting. Crystals grown from
The support of this work by the German Research Council (DFG) within the Collaborative Research Area SFB 813
is gratefully acknowledged. We thank Dr. J. Daniels for the
collection of X-ray diffraction data, N. Wagner for his efforts
with the conductivity measurements and S. von Erichsen for
assistance in the synthetic work.
[1] G. Stenhouse, Proc. Royal Soc. London 1868, 17, 62 –
72.
[2] K. L. Gallaher, S. H. Bauer, J. Chem. Soc., Faraday
Trans. 2, 1975, 71, 1173 – 1182.
[3] S. B. Larson, S. H. Simonsen, G. E. Martin, K. Smith,
S. Puig-Torres, Acta Crystallogr. 1984, C40, 103 – 106.
[4] M. E. Amato, A. Grassi, K. J. Irgolic, G. C. Pappalardo,
L. Radics, Organometallics 1993, 12, 775 – 780.
[5] V. S. Mastryukukov, K.-H. Chen, S. H. Simonsen, N. L.
Albinger, J. E. Boggs, J. Mol. Struct. 1997, 413 – 414,
1 – 12.
[6] A. Ito, H. Ino, H. Ichiki, K. Tanaka, J. Phys. Chem. A
2002, 196, 8716 – 8720.
[7] S. Kim, Y. Kwon, J.-P. Lee, S.-Y. Choi, J. Choo, J. Mol.
Struct. 2003, 655, 451 – 458.
[8] J. V. de Vondele, R. Lyriden-Bell, E. J. Meyer,
M. Sprik, J. Phys. Chem. B 2006, 110, 3614 – 3623.
[9] E. A. C. Lucken, J. Chem. Soc. 1962, 4963 – 4965.
[10] W. Rundel, L. Scheffler, Tetrahedron Lett. 1963, 993 –
995.
[11] Y. Murata, L. Hughes, H. J. Shine, Inorg. Nucl. Chem.
Lett. 1968, 4, 573 – 576.
[12] Y. Sato, M. Kinoshita, M. Sano, H. Akamatu, Bull.
Chem. Soc. Jpn. 1967, 40, 2539 – 2542.
[13] B. K. Bandlish, H. J. Shine, J. Org. Chem. 1977, 42,
561 – 563.
[14] H. Bock, A. Rauschenbach, Ch. Näther, M. Kleine,
Z. Havlas, Chem. Ber. 1994, 127, 2043 – 2049.
[15] M. de Sorgo, B. Wassermann, M. Szwarc, J. Phys.
Chem. 1972, 76, 3468 – 3471.
[16] P. Rapta, L. Kress, P. Hapiot, L. Dunsch, Phys. Chem.
Chem. Phys. 2002, 4, 4181 – 4185.
[17] S. V. Rosokha, J. Lu, T. J. Rosokha, J. K. Kochi, Acta
Crystallogr. 2007, C63, o347–o349.
[18] L. A. Tinker, A. J. Bard, J. Am. Chem. Soc. 1979, 101,
2316 – 2319.
[19] O. Hammerich, V. D. Parker, Electrochim. Acta 1973,
18, 537 – 541.
[20] G. Gritzner, J. Kuta, Pure & Applied Chem. 1984, 56,
461 – 466.
[21] H. Bock, A. Rauschenbach, K. Ruppert, Z. Havlas,
Angew. Chem. 1991, 103, 706 – 708; Angew. Chem.,
Int. Ed. Engl. 1991, 30, 714 – 716.
[22] T. Nishinaga, K. Komatsu, Org. Biomol. Chem. 2005,
3, 561 – 569.
[23] R. Dovesi, V. R. Saunders, C. Roetti, R. Orlando, C. M.
Zicovich-Wilson, F. Pascale, B. Civalleri, K. Doll,
N. M. Harrison, I. J. Bush, Ph. D’Arco, M. Llunell,
X-Ray structure determination
Unauthenticated
Download Date | 6/16/17 4:35 AM
152
J. Beck et al. · Thianthrene Radical Cation Hexafluorophosphate
C RYSTAL 06, User’s Manual, University of Torino,
Torino (Italy) 2006.
[24] A. Schäfer, C. Huber, R. Ahlrichs, J. Chem. Phys.
1994, 100, 5829 – 5835.
[25] T. Bredow, A. R. Gerson, Phys. Rev. B 2000, 61, 5194 –
5201.
[26] F. Cora, M. Alfredsson, G. Mallia, D. S. Middlemiss,
W. C. Mackrodt, R. Dovesi, R. Orlando, Struct. Bond.
2004, 113, 171 – 232.
[27] J. P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett.
1996, 77, 3865 – 3868.
[28] J. Beck, F. Steden, Z. Naturforsch. 2003, 58b, 711 –
714.
[29] J. Ghilane, P. Haplot, A. J. Bard, Anal. Chem. 2006, 78,
6868 – 6872.
[30] G. M. Sheldrick, S HELXS / L -97 (release 97-2), Programs for Crystal Structure Determination, University
of Göttingen, Göttingen (Germany) 1997.
[31] R. H. Blessing, Acta Crystallogr. 1995, A51, 33 – 38.
Unauthenticated
Download Date | 6/16/17 4:35 AM